When Do Guys Stop Growing? Ages, Signs and What Decides It

When do guys stop growing? What decides it

Three things set the answer to when do guys stop growing for each boy: when puberty starts, when his growth plates close, and the genes he got from his parents. Jump to the part you need: puberty timing, growth plates or genes.

Puberty timing. The American Academy of Pediatrics (AAP) explains that children who enter puberty earlier often have a growth spurt sooner but may stop growing at a younger age. Those who enter puberty later may keep growing for longer.

Growth plates. MedlinePlus describes a growth plate as the cartilage plate near the end of the bone of a growing child where growth occurs. The AAP says that once a child finishes puberty and the growth plates close, he can no longer grow taller.

Genes. The AAP says about 60% to 70% of differences in height are set by the parents’ height. The same AAP page lists nutrition, sleep and activity among the other things that affect growth.

Puberty timeline for boys

Puberty is a long process, and it is the biggest clue to when do guys stop growing. It does not start or end on the same day for every boy. This table puts the main steps in order.

Step	What the sources say
First signs of puberty	95% of boys start between ages 9 and 14 (AAP)
Growth spurt begins	About a year after the first signs, generally by age 15 (AAP)
Peak growth speed	Later in puberty. In a 1970 study, the 41 boys measured for it peaked at 14.1 years on average
Voice change	Just after the peak of the growth spurt (AAP)
Puberty complete	3.5 to 4 years after it starts (MedlinePlus)

The fast part can be dramatic. Boys may grow four inches in 12 months and add 13 to 14 inches over three to four years, says the AAP. Boys also trail girls by about two years. For more on this stage, see our guide to the growth spurt.

The 1970 study is old, so treat its numbers as a guide, not a rule.

Growth plates: what they are and when they close

Growth plates are where a growing bone gets longer. So when do guys stop growing? When these plates close. In a 2020 MRI study of 958 healthy people aged 14.0 to 21.5, plates fused in order “from the foot to the wrist.” Fusion came about two years earlier in girls than in boys.

Here is how many 19 year old males had complete fusion at each site.

Site	Complete fusion in 19 year old males
Radius (forearm bone at the wrist)	90%
Femur (thigh bone)	97%
Proximal tibia (shin bone, near the knee)	95%
Distal tibia (shin bone, near the ankle)	97%
Calcaneus (heel bone)	98%

So by 19, most plates are closed, but not all of them in every guy. The study also found that regular physical activity was not linked to how mature the plates were. Overweight people had more mature plates than their peers. Read more in our guide to growth plates.

Can guys keep growing after 18?

So when do guys stop growing for good? For most, by the late teens. Yes, some do keep growing after 18, by a small amount. A 1983 study followed 221 Polish boys. Only 54% were within 1 cm of the same height at 27 as at 19. The average gain in height was 2.13 cm (about 0.8 inch) and the biggest was 7 cm (about 2.8 inches), according to the study abstract. It is an old group of boys, so use it as a rough picture.

	AAP	1983 study of 221 boys
What it says	Most teens grow no more than another inch or two after puberty	Average gain of 2.13 cm in the late teens and twenties, up to 7 cm
Who is affected	Teens who have finished puberty	46% were not within 1 cm of their height at 19

What about growing taller after puberty? Once the plates close, the AAP says a child can no longer grow taller. Our guide on how to grow taller covers what is and is not possible.

How to tell if a boy is still growing

Parents often ask when do guys stop growing for their own son. There is no home test. You can look for clues, but only a doctor can confirm that growth plates are closed.

Signs he is still growing

• Puberty is still in progress. Puberty takes 3.5 to 4 years, so a boy who started at 12 may still be developing at 15.
• His voice has not changed yet. The AAP says the voice box grows just after the peak of the growth spurt.
• His height keeps rising from one checkup to the next.

Signs growth is finishing

• Puberty is complete, which takes 3.5 to 4 years from the start.
• His voice has changed, which the AAP places just after the peak of the growth spurt.
• His height stays the same across several checkups.

Using a growth chart

The CDC offers growth charts with a boys’ stature for age chart that covers ages 2 to 20. Plot his height at each birthday and look at the line over time. These are percentile curves that show how body measurements are spread across U.S. children. The CDC says growth charts are “not intended to be used as a sole diagnostic instrument,” so use the chart to spot a trend, not to make a diagnosis.

Genetics, nutrition and sleep

Genetics

The AAP says about 60% to 70% of height differences come from the parents’ height. A pooled analysis of 45 twin groups (180,520 paired measurements, ages 1 to 19) found that the genetic share of height rose with age, up to 0.83 in boys in adolescence.

The AAP gives a formula to estimate a boy’s adult height: (mother’s height + 5 inches + father’s height) divided by 2. It adds that you can expect a margin of error of about 4 inches up or down.

Nutrition

The AAP says good nutrition is essential for healthy growth. The Endocrine Society says that outside the treatable causes it lists, there is no specific food, diet or exercise that can improve growth. Neither source lists a supplement that raises height in a healthy child.

If you are weighing a growth gummy, see our pick below. For the facts first, read what the evidence says about growth gummies.

Sleep

A 2024 review says growth hormone release mostly happens during deep sleep. The same review calls the nine studies it found on sleep in children with growth hormone deficiency “limited, old/poor quality, and heterogenous/inconsistent.” So sleep matters for health, but nothing here shows that extra sleep adds inches. See our guide on sleep and growth.

Late bloomers

When do guys stop growing if they start puberty late? Later than their friends. Some boys start puberty late, and nothing is wrong. Doctors call this constitutional delay of growth and puberty. The AAP says it is the most common cause of delayed puberty and is inherited from one or both parents in about two thirds of cases.

Two views are worth knowing.

• The reassuring view. The AAP says these boys usually catch up to other boys by 18 and have heights in the normal range as adults. The Endocrine Society says they reach a normal adult height.
• The cautious view. A small 2018 study of 15 boys with constitutional delay found final or near final heights of 165.7 cm on average, below their target of 171.8 cm. That is a gap of about 6 cm, or 2.4 inches. The authors name the small sample as the study’s limitation, so treat it as a counterpoint, not a rule.

The AAP adds that a short course of testosterone has no effect on adult height. It only helps the boy get there faster.

When to see a doctor

Start with your pediatrician. They can plot his growth and decide whether more tests are needed.

What a bone age X-ray is

If you want a closer answer on when do guys stop growing for one boy, ask about a bone age X-ray. It is a picture of the left hand and wrist. The Endocrine Society says it is used to determine the maturity of the bony growth plates. In constitutional delay, the AAP says bone age is typically at least 2 years behind the child’s age, which means more time remains for growth.

The AAP calls current height together with a bone age assessment the most accurate method of height prediction. It is still a prediction, not a promise.

What to remember

When do guys stop growing? It depends on when puberty starts, so the age differs from boy to boy. Track height on a chart and see a doctor if something looks off. The answer to when do guys stop growing is a range, not a date. For the wider picture on growing kids and teens, see our guide to vitamins for kids.

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